Abstract

It is generally believed that, in the phenomena of extraordinary optical transmission, perfect transparency only occurs at a single or a multiple of discrete frequencies. This report presents for the first time that a stacked metallic multi-layered system, being perforated with coaxial annular apertures (CAAs), can be perfectly transparent in a broad frequency range. The phenomenon arises from the coupling of guided resonance modes in CAAs among different metallic layers. The transparency bandwidth is extended to about 40% of the central frequency with only 2–3 metallic layers. Measured transmission spectra in microwave regime are in good agreement with calculations which are semi-analytically resolved by modal expansion method.

(a) Dispersion relation of bulk material periodically constructed by layered CAAs. The inset shows a unit cell of the bulk material. (b) The frequencies of resonant modes (transmission peaks) for the n =1, 2 and 3 models. The thin lines denote the process of mode splitting. fA = 8.7GHz and f′A = 12.1GHz refer to the frequencies of the transmission peaks of the n = 1 sample with and without dielectric layer.